Vehicles, such as commercial and industrial vehicles, utilize speed sensors to detect the rotational speed of one or more components within an engine, or elsewhere on the vehicle during operation of the vehicle. The output of the speed sensor is, in some examples, provided to a differential comparator and the differential comparator provides a readable output to a microprocessor indicating when the speed has exceeded a pre-determined threshold. Based on the readable output, the microprocessor generates controls, thereby controlling the rotating component or any other system within the vehicle.
In existing interface circuits for connecting the output of a speed sensor to a microprocessor, the magnitude of the hysteresis used in the processing of the sensor signal is increased in correspondence with a speed increase. Variable reluctance speed sensors, and sensors that operate in a similar fashion to variable reluctance speed sensors, have an output signal with a magnitude that increases in correspondence with an increase in speed. As a result, at zero or low speeds, the output of a variable reluctance speed sensor can be difficult to distinguish from noise on the output signal line, and a greater hysteresis is required. In contrast, at high speeds, the magnitude of the output signal is significantly larger than the noise, and minimal hysteresis is required to interpret the signal.